ALEXANDRIA, VA. — A U.S. Army veteran was confused and mistaken when he told authorities he fought with an al-Qaida group seeking to topple the regime of Syrian President Bashar Assad, his defense lawyer said Wednesday in court papers.

In March, federal prosecutors in Alexandria charged Eric Harroun, 30, of Phoenix, with using a rocket propelled grenade as a soldier in the Nusra Front, which the State Department says is an alias for al-Qaida in Iraq. Harroun faces up to life in prison if convicted.

But in court papers filed Wednesday, Harroun’s lawyer, federal public defender Geremy Kamens, says that while Harroun may have thought he had joined up with Jabhat al-Nusra, the facts demonstrate otherwise. The motion states Harroun spoke only a few words of Arabic and was not well-versed on the jumble of groups arrayed in the fight against Assad.

“The government is wrong,” Kamens wrote. “In sum, the government made a mistake in deciding to arrest and charge Mr. Harroun before it could corroborate his statements that he fought with Jabhat al Nusra.”

The motion seeks Harroun’s release from jail while he awaits trial. It was filed two days before a deadline for the government to file its indictment against Harroun, which could potentially include additional details of the government’s case.

In an FBI affidavit filed with the original charges in March, the government said that Harroun told investigators he went to Syria in January with the intention of joining the Free Syrian Army, one of the main umbrella opposition groups and one that carries no terrorist designation.

Harroun told the FBI that he participated with the Free Syrian Army in a battle, but during a retreat ended up getting a ride in a Nusra Front truck. Harroun said that the Nusra Front initially treated him skeptically — more like a prisoner — but he eventually gained their trust and participated in several battles with them, according to the affidavit.

Most of the evidence in the affidavit linking Harroun to the Nusra Front comes from voluntary interviews Harroun gave to the FBI.

Harroun, who received a medical discharge from the Army after suffering a severe head injury, openly bragged about his adventures in Syria. He gave media interviews in which he was quoted saying that joining the Nusra Front “is not rocket science,” but at other times he gave conflicting statements about whether he had a connection with the group.

In the defense motion filed Wednesday, Kamens wrote that Harroun “speaks only a few words of Arabic, and has no particular familiarity with the various opposition groups in Syria.” The defense also supplied affidavits from two Middle East experts who suggest that the Nusra Front is a highly secretive fundamentalist group that would be unwilling to accept an American into its ranks, especially one like Harroun who openly smoked and drank alcohol.

While the Nusra Front is designated a terrorist group by the U.S., the Free Syrian Army enjoys U.S. support, and Kamens said that Harroun committed no crime by joining them.